Honeycomb structure and process for production thereof

ABSTRACT

There is provided a honeycomb structure in which the structure is not segmented, or a smaller number of segments are integrated to suppress a local temperature rise and to reduce breakage by thermal stress at the time of use, and a method of manufacturing the structure. There is disclosed a honeycomb structure  1  comprising: a large number of cells  3  partitioned by cell walls  2  and extending through an axial direction. A flow channel separator  6  is formed in the honeycomb structure  1 . There is disclosed a method of manufacturing the honeycomb structure  1  in which the flow channel separator  6  is formed by extrusion. There is disclosed a method of manufacturing the honeycomb structure  1  in which the flow channel separator  6  is formed by clogging.

TECHNICAL FIELD

The present invention relates to a honeycomb structure for use in afilter for capturing particulates in an exhaust gas of an internalcombustion engine or a boiler, and a method of manufacturing thestructure, particularly to a honeycomb structure which is hardly damagedby a thermal stress at the time of use and which can be manufactured byan economically advantageous process, and the method of manufacturingthe structure.

BACKGROUND ART

A honeycomb structure has been used in a filter for capturingparticulate in exhaust gas of an internal combustion engine or a boiler,particularly used in a filter for capturing diesel particulate (it ishereinafter referred to as DPF) or a substrate for purifying exhaustgas, or the like.

The honeycomb structure for use in this purpose, in general, includes alarge number of cells 3 partitioned by cell walls 2 and extendingthrough an X-axis direction as shown in FIGS. 18( a) and 18(b).Furthermore, the structure for the DPF usually includes a structure inwhich the cells 3 disposed adjacent to each other are alternatelyplugged at ends on opposite sides so that end surfaces form checkeredpatterns. In such a honeycomb structure, a fluid to be treated flows inthe cell 3 not plugged at inflow end face 42, that is, plugged atoutflow end face 44, passes through the porous cell walls 2, and isdischarged via the adjacent cells 3, that is, the cell 3 plugged at theinflow end face 42 and not plugged at outflow end face 44. In this case,the cell walls 2 act as a filter. For example, soot discharged from adiesel engine is trapped by the cell walls and deposited on the cellwalls. In a honeycomb structure used in such a way, the sharptemperature change of exhaust gas and the local heating of the structuremake non-uniform the temperature distribution inside the structure andthere have been problems such as crack generation in honeycomb structureand the like. When the honeycomb structure is used particularly as aDPF, it is necessary to burn the fine carbon particles deposited on thefilter to remove the particles and regenerate the filter and, in thatcase, high temperatures are inevitably generated locally in the filter;as a result, a big thermal stress and cracks have tended to generate.

To solve the problem, a method of bonding a plurality of dividedsegments of the honeycomb structure by a bond material has beenproposed. For example, in U.S. Pat. No. 4,335,783, a method formanufacturing a honeycomb structure is disclosed in which a large numberof honeycomb members are bonded by discontinuous bond materials. Also inJP-B-61-51240 is proposed a thermal-shock resistant rotary regeneratingthermal exchanging method which comprises forming, by extrusion, matrixsegments of honeycomb structure made of a ceramic material, firing them,making smooth, by processing, the outer peripheral portions of the firedsegments, coating the to-be-bonded areas of the resulting segments witha ceramic adhesive having, when fired, substantially the same chemicalcomposition as the matrix segments and showing a difference in thermalexpansion coefficient, of 0.1% or less at 800° C., and firing the coatedsegments. In SAE document 860008 of 1986, a ceramic honeycomb structureis disclosed in which the honeycomb segment of cordierite is similarlybonded with cordierite cement. Further in JP-A-8-28246 is disclosed aceramic honeycomb structure obtained by bonding honeycomb ceramicmembers with an elastic sealant made of at least a three-dimensionallyintertwined inorganic fiber, an inorganic binder, an organic binder andinorganic particles.

A method in which a plurality of segments divided in this manner areintegrated to suppress a local temperature rise is an effective method.However, this requires a step of producing many segments and thereafterintegrating these segments in order to manufacture one honeycombstructure, and this is not economically favorable especially in a casewhere the structure needs to be divided into a large number of segments.

The present invention has been developed in consideration of thesituations, and an object thereof is to provide a honeycomb structurewhich is not segmented or is integrally constituted of a smaller numberof segments to suppress a local temperature rise and to reduce damagesby a thermal stress at the time of use, and a method of manufacturingthe honeycomb structure.

DISCLOSURE OF THE INVENTION

According to the present invention, there is provided a honeycombstructure including a large number of cells partitioned by cell wallsand extending through an axial direction, characterized in that a flowchannel separator is formed.

In the present invention, at least an inflow port end is preferablysealed to form the flow channel separator. Moreover, for the honeycombstructure of the present invention, a thermal expansion coefficient at20° C. to 800° C. is preferably 2×10⁻⁶/° C. or more. A plurality ofhoneycomb structural segments are integrated to constitute the honeycombstructure, and the flow channel separator is preferably formed in atleast one of the honeycomb structural segments. Furthermore, thehoneycomb structure preferably includes a honeycomb structural segmentin which a sectional area of the cell in a vertical direction is 900 mm²to 10000 mm² Furthermore, a bonding material whose difference from thehoneycomb structural segment in the thermal expansion coefficient is1.5×10⁻⁶/° C. or less is used to bond and integrate the honeycombstructural segments. Furthermore, the honeycomb structure of the presentinvention is preferably formed of one or two or more materials selectedfrom a group consisting of silicon nitride, silicon carbide, asilicon-silicon carbide based composite material, mullite, a siliconcarbide-cordierite based composite material, and alumina.

Furthermore, according to the present invention, there is provided amethod of manufacturing a honeycomb structure including a large numberof cells partitioned by cell walls and extending through an axialdirection, wherein a flow channel separator is formed, the methodcharacterized by: forming the flow channel separator by extrusion.

Additionally, according to the present invention, there is provided amethod of manufacturing a honeycomb structure including a large numberof cells partitioned by cell walls and extending through an axialdirection, wherein a flow channel separator is formed, the methodcharacterized by: forming the flow channel separator by clogging.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a schematic perspective view of a honeycomb structure ofthe present invention, FIG. 1( b) is a schematic plan view, and FIG. 1(c) is a schematic side view.

FIG. 2( a) is a schematic sectional view of a II—II arrow section inFIG. 1( c), FIG. 2( b) is a partially enlarged view of FIG. 2( a), andFIG. 2( c) is a partially enlarged view showing another embodiment ofthe present invention.

FIG. 3( a) is a schematic plan view in one embodiment of the honeycombstructure of the present invention, and FIG. 3( b) is the enlarged view.

FIG. 4( a) is a schematic plan view in one embodiment of the honeycombstructure of the present invention, and FIG. 4( b) is the enlarged view.

FIG. 5( a) and 5(b) are schematic perspective views showing one exampleof a segmented honeycomb structure.

FIGS. 6( a), 6(b), 6(c), and 6(d) are schematic plan views each showingone embodiment of the honeycomb structure of the present invention.

FIG. 7 is a schematic top view of the honeycomb structure produced inExample 1.

FIG. 8 is a schematic top view of the honeycomb structure produced inExample 2.

FIG. 9 is a schematic top view of the honeycomb structure produced inExample 3.

FIG. 10( a) is a schematic perspective view of the honeycomb structureproduced in Comparative Example 1, and FIG. 10( b) is a schematicperspective view of the segment.

FIG. 11 is a schematic top view of the honeycomb structure produced inExample 4.

FIG. 12 is a schematic top view of the honeycomb structure produced inExample 5.

FIG. 13 is a schematic top view of the honeycomb structure produced inExample 6.

FIG. 14( a) is a schematic perspective view of the honeycomb structureproduced in Comparative Example 2, and FIG. 14( b) is a schematicperspective view of the segment.

FIG. 15 is a schematic top view of the honeycomb structure produced inExample 7.

FIG. 16 is a schematic top view of the honeycomb structure produced inExample 8.

FIG. 17( a) is a schematic perspective view of the honeycomb structureproduced in Comparative Example 3, and FIG. 17( b) is a schematicperspective view of the segment.

FIG. 18( a) is a schematic perspective view showing a conventionalhoneycomb structure; and FIG. 18( b) is a partially enlarged top view ofFIG. 18( a).

BEST MODE FOR CARRYING OUT THE INVENTION

Contents of a honeycomb structure and a method of manufacturing thestructure according to the present invention will hereinafter bedescribed in accordance with examples of the honeycomb structure for DPFin detail with reference to the drawings, but the present invention isnot limited to the following embodiment. Incidentally, in the following,“section” refers to a section vertical to the longitudinal direction ofcells (X-axis direction) unless otherwise specified.

FIGS. 1( a) to 1(c) and FIGS. 2( a), (b) are schematic diagrams showingone embodiment of the honeycomb structure of the present invention. InFIGS. 1( a), 1(c) and FIGS. 2( a) to 2(c), an upper side constitutes aninflow port end 42, that is, an end of inflow of a fluid to be treatedsuch as an exhaust gas. The honeycomb structure of the present inventionincludes a large number of cells 3 partitioned by cell walls 2 andextending through an axial direction. Further in the honeycomb structurefor DPF shown in FIGS. 1( a) to 1(c) and FIGS. 2( a), 2(b), the cells 3disposed adjacent to each other in ends 31 of cells are alternatelyclogged at ends on opposite ends by a clogging material 5. Importantcharacteristics of the present invention lie in that a flow channelseparator 6 is formed in the honeycomb structure. The flow channelseparator is a layer which substantially prevents the fluid to betreated of one cell 3 from flowing into the other cell 3 or largelyinhibits the flowing in the cells 3 disposed on opposite sides of theflow channel separator 6. It is to be noted that the flow channelseparator in the present application is different from a bond layerformed for bonding a segmented/divided honeycomb structure, and the bondlayer is excluded from the flow channel separator of the presentapplication. When the flow channel separator 6 is disposed, the fluid issubstantially prevented or inhibited from flowing via the flow channelseparator 6, and a flow channel of the fluid to be treated is separatedby the flow channel separator 6. Furthermore, the flow channel separator6 constitutes an insulating layer, and inhibits heat from moving via theflow channel separator 6. When the flow channel separator has asufficient heat capacity, the separator performs a function of absorbingcombustion heat of soot or contributing to thermal diffusion to controlrapid soot combustion. By these effects, chain combustion of theaccumulated soot is inhibited, and thermal burn-up by explosivecombustion of soot can be prevented, when the honeycomb structure of thepresent invention is used especially as the DPF. Since this effect isobtained by the flow channel separator, it is possible to reducebreakage by thermal stress without dividing the honeycomb structure intosegments or with a smaller number of divisions. It is to be noted thatthe above-described effects of the flow channel separator are moreeffectively obtained, when the honeycomb structure is used as the DPF.However, needless to say, the effects of the present invention can alsobe obtained, for example, in other applications, for example, with theuse as a catalyst carrier or another filter.

As shown in FIGS. 1( b) and 2(b), the inflow port end 42 can linearly besealed to form the flow channel separator. In this case, a layer of airis formed in an X-axis direction along a line of the sealed flow channelseparator 6 shown in FIG. 1( b), and this performs the function of theflow channel separator. In this case, it is also preferable to furtherseal an outflow port end 44 from the standpoint of insulation and aninterrupting property of flow circulation. Furthermore, as shown in FIG.2( c), a member of ceramic, and the like may also be charged over theX-axis direction to form the flow channel separator. Moreover, themember of ceramic, and the like may also be charged in a part of theX-axis direction to form the flow channel separator. In a case where theinflow port end 42 and preferably further the outflow port end 44 aresealed in order to form the flow channel separator 6, examples of thesealing material include a ceramic and/or a metal similar to materialssuitable for the honeycomb structure described later. In this case, thematerial similar to that selected from these for actual use in thehoneycomb structure is preferably used as the material of the sealingmaterial. It is also possible to use the material different from that ofthe honeycomb structure in the sealing material. In this case, thethermal expansion coefficient may be approximated to that of thematerial of the honeycomb structure, and a difference in the thermalexpansion coefficient is preferably set, for example, to 1×10⁻⁶/° C. orless.

In the present invention, a width of the flow channel separator is notespecially limited, but the effect of the present invention is noteasily obtained with an excessively small width. With an excessivelylarge width, a treatment capacity of the honeycomb structure decreases,or a soot reproduction efficiency with the use in the DPF drops, whichis unfavorable. The width of the flow channel separator is preferably300 μm to 3000 μm, more preferably 400 μm to 2000 μm, most preferably500 μm to 1000 μm. This range is determined by a cell structure of thehoneycomb structure for use, but the width is preferably larger than acell wall thickness of the honeycomb structure by 50 μm or more.

A length of the flow channel separator or the number of separators isnot especially limited, and can be selected in a range in which thebreakage by the thermal stress does not easily occur, the treatmentcapacity of the honeycomb structure hardly decreases, and the sootreproduction efficiency with the use in the DPF hardly drops by a personskilled in the art in accordance with a material, size, or applicationof the honeycomb structure. Additionally, from the standpoint of theinsulating effect or the inhibition of chain reaction, as shown in FIGS.3( a), 3(b), 4(a), and 4(b), the honeycomb structure is preferablypartitioned into a plurality of structures by the flow channelseparators. FIGS. 3( a) and 3(b) show the flow channel separator 6formed by sealing through holes by a sealing process described later,and FIGS. 4( a) and 4(b) show the flow channel separator 6 formed by anintegral forming method described later. Since a section central part ofthe honeycomb structure easily have a higher temperature, more flowchannel separators 6 are preferably disposed in the central part.

The honeycomb structure of the present invention in which the flowchannel separators 6 are formed is effective especially with a largethermal expansion coefficient. The honeycomb structure of the presentinvention is more effective, when the thermal expansion coefficient at20° C. to 800° C. is preferably 2×10⁻⁶/° C., more preferably 2.5×10⁻⁶/°C., most preferably 3×10⁻⁶/° C. Concretely, the present invention isespecially effective in a honeycomb structure of a silicon carbidematerial or a silicon-silicon carbide composite material at a level ofthermal expansion coefficient of 4×10⁻⁶/° C.

For the honeycomb structure of the present invention, as shown in FIGS.5( a) and 5(b), a plurality of divided segments 12 may be bonded by abonding material 8. In this case, the flow channel separator may bedisposed in any of the divided segments 12, and various forms of flowchannel separators 6 may be disposed as shown in FIGS. 6( a) to 6(d).When the flow channel separators are disposed in this manner, thebreakage by the thermal stress can be prevented. Therefore, even in acase where it has heretofore been necessary to divide the structure intofurther smaller segments, the similar effect can be obtained withoutdividing the structure into the small segments. Also in this case, forthe same reason as described above, the flow channel separators arereduced or are not disposed in the segments on an outer peripheralportion of the honeycomb structure, and more flow channel separators arepreferably disposed in the segments in the central part.

As described above, a plurality of honeycomb segments are integratedusing the bonding material 8. However, when the difference of thethermal expansion coefficient between the bonding material 8 and thehoneycomb segment 12 is excessively large, the thermal stress isunfavorably concentrated onto a bonded portion at the time ofheating/cooling. The difference of the thermal expansion coefficientbetween the bonding material and the honeycomb segment at 20° C. to 800°C. is preferably 1.5×10⁻⁶/° C., more preferably 1×10⁻⁶/° C., morepreferably 0.8×10⁻⁶/° C. or less. A preferable bonding material can beselected from the materials for use preferably as the major component ofthe honeycomb structure described later. Moreover, when the sectionalarea of each segment is excessively small, a necessity for the disposingof the flow channel separators of the present invention lowers. Anexcessively large sectional area is not preferable because the area ofthe separator is large with respect to the sectional area and a pressureloss increases. In the present invention, the sectional area of thehoneycomb segment is preferably 900 mm² to 10000 mm², more preferably950 mm² to 5000 mm², most preferably 1000 mm² to 2500 mm². A shape ofthe honeycomb segment is not especially limited, but a square pole shapeshown in FIG. 5( b) is assumed to be a basic shape, and the shape of thehoneycomb segment on the outer peripheral side can appropriately beselected in accordance with the shape of the honeycomb structureintegrated as shown in FIG. 5( a).

In the present invention, from the standpoint of strength, heatresistance, and the like, major components of a honeycomb structure 1preferably include at least one material selected from a groupconsisting of cordierite, mullite, alumina, spinel, silicon carbide,silicon carbide-cordierite based composite material, silicon-siliconcarbide based composite material, silicon nitride, lithium aluminumsilicate, aluminum titanate, Fe—Cr—Al based metal, and a combination ofthese. Silicon carbide or silicon-silicon carbide based compositematerial high in thermal conductivity is especially preferable in thatheat is easily radiated. Especially, silicon carbide is preferablebecause heat is easily radiated, and is also suitable especially for thehoneycomb structure of the present invention in that a measure for thethermal stress is required in a case where the thermal expansioncoefficient is comparatively large and the temperature locally rises.Here, it is meant that the “major component” constitutes 50% by mass ormore, preferably 70% by mass or more, further preferably 80% by mass ormore of the honeycomb structure.

In the present invention, for the honeycomb structure formed of metalsilicon (Si) and silicon carbide (SiC), when an Si content defined bySi/(Si+SiC) is excessively small, an effect of Si addition cannot beobtained. When the Si content exceeds 50% by mass, the effects ofcharacteristics of SiC such as heat resistance and high thermalconductivity is hardly obtained. The Si content is preferably 5 to 50%by mass, further preferably 10 to 40% by mass.

In the present invention, the cell wall 2 of the honeycomb structure 1is preferably a porous body which performs a function of a filter or acatalyst carrier as described above. A thickness of the cell wall 2 isnot especially limited. However, when the cell wall 2 is excessivelythick, the treatment capacity of the fluid to be treated drops or alarge pressure loss is caused. When the cell wall 2 is excessively thin,the strength of the honeycomb structure becomes insufficient, and theexcessive thickness is unfavorable. The thickness of the cell wall 2 isin a range of preferably 100 to 1000 μm, more preferably 150 to 750 μm,most preferably 250 to 500 μm.

In the honeycomb structure of the present invention, there is noparticular restriction as to the sectional shape of cell (cell shape);however, the sectional shape is preferably any of a triangle, atetragon, a hexagon and a corrugated shape from the standpoint ofproduction. Moreover, a cell density, that is, the number of cells 3(cells) per unit area on the section of the honeycomb structure 1 is notespecially limited. However, when the cell density is excessively small,the strength or effective filter area of the honeycomb structure becomesinsufficient. When the cell density is excessively large, the pressureloss increases in a case where the fluid to be treated flows.

The cell density is in a range of preferably 50 to 1000 cells/in.² (7.75to 155 cells/cm²), more preferably 75 to 500 cells/in.² (11.6 to 77.5cells/cm²), most preferably 100 to 400 cells/in.² (15.5 to 62.0cells/cm²). The sectional shape of the honeycomb structure of thepresent invention is not especially limited, and any shape may be usedsuch as a polygonal shape including an ellipse, an elongated circle, anoval, a substantial triangle, or a substantial tetragon, in addition toa circle.

When the honeycomb structure of the present invention is to be used as acatalyst substrate for purifying the exhaust gas of thermal engines suchas an internal combustion engine or combustion apparatuses such as aboiler, or for modifying a liquid or gas fuel, a catalyst such as ametal having a catalytic capability is preferably loaded on thehoneycomb structure of the present invention. Examples of a typicalmetal having the catalytic capability include Pt, Pd, Rh, and at leastone of these is preferably loaded on the honeycomb structure.

In the honeycomb structure of the present invention, the cells 3disposed adjacent to each other are preferably alternately clogged atends on the opposite sides, so that the end surfaces 42 and 44 havecheckered patterns, and the ceramic or the metal that can preferably beused in the above-described honeycomb structure can preferably be usedin the material for use in the clogging.

Next, a method for manufacturing the honeycomb structure of the presentinvention will be described.

As a raw material powder of the honeycomb structure, the above-describedpreferable materials such as a silicon carbide powder are used. To thepowder, binders such as methyl cellulose and/or hydroxypropoxyl methylcellulose are added. Further a surfactant and water are added to preparepuddle having plasticity. When the puddle is extruded/molded, as shownin FIGS. 2( c), 4(a), and 4(b), the honeycomb structure is obtainedincluding the flow channel separator into which the puddle is charged ata certain width, for example, at a width of 500 μm.

The honeycomb structure is dried, for example, by microwave and hot air.Thereafter, the cells 3 are plugged at one end alternately, with amaterial similar to that for use in manufacturing the honeycombstructure, so that the end faces have checkered patterns. The segmentwas dried further, then heated and degreased in, for example, an N₂atmosphere, and fired in for example an Ar inert atmosphere, so that thehoneycomb structure according to the present invention can be obtained.A method of forming the flow channel separator at the time of extrusionin this manner will hereinafter be referred to as an integral formingmethod.

Furthermore, in another method of manufacturing the honeycomb structureof the present invention, after preparing the puddle as described above,the puddle is extruded/molded to mold the honeycomb structure shown, forexample, in FIGS. 18( a) and 18(b).

For example, this structure is dried by microwave and hot air, andthereafter the cells disposed adjacent to each other are alternatelyclogged at the ends on the opposite sides by the material similar tothat used in manufacturing the honeycomb structure, so that end surfaceshave the checkered patterns. In this case, as shown in FIGS. 2( b),3(a), and 3(b), a series of consecutive through holes are sealedaltogether, further dried, heated/degreased, for example, in an N₂atmosphere, and thereafter fired in an inactive atmosphere of Ar, andthe like. Accordingly, the sealed through holes continuously arranged inone row form the layer of the flow channel separator, and the honeycombstructure of the present invention can be obtained. A method of formingthe flow channel separator by the sealing after the molding willhereinafter be referred to as a sealing method. In this case, thethrough holes for forming the flow channel separator may have shapesdifferent from those of the usual cells, and are preferably narrowedbeforehand as compared with the other cells, for example, as shown inFIG. 2( b).

When a plurality of segments are integrated to manufacture the honeycombstructure of the present invention, the honeycomb segments are prepared,for example, in any of the above-described methods. The honeycombsegments are bonded, for example, using a ceramic cement containingceramic fiber and ceramic as the major components in the bondingmaterial, thereafter dried, and fired in the same manner as describedabove so that the honeycomb structure of the present invention can beobtained.

For the honeycomb structure manufactured in such various ways, a methodfor loading a catalyst may be a method usually carried out by a personskilled in the art. For example, the catalyst can be loaded on thestructure by wash-coating of the catalyst slurry, subsequently dryingand firing.

The present invention will be described hereinafter in further detailbased on examples, but the present invention is not limited to theseexamples.

EXAMPLE 1

As a raw material, a mixed powder containing 80% by mass of SiC powderand 20% by mass of metal Si powder was used. To the powder, methylcellulose, hydroxypropoxyl methyl cellulose, surfactant, and water wereadded to prepare the puddle having plasticity. This puddle was subjectedto extrusion molding, the extrudate was dried using a microwave and hotair to obtain a honeycomb segment having a cell wall thickness of 380μm, a cell density of 200 cells/in.² (31.0 cells/cm²), a fun-shapedsection which is ¼ of a circle of 144 mm in diameter and a length of 152mm. In this case, to alternately clog the adjacent cells at the ends onthe opposite sides with the material similar to that used inmanufacturing the honeycomb structure so that the end surfaces have thecheckered patterns, as shown in FIG. 7, the cells continuously arrangedin one row are sealed together as shown in FIG. 7, dried, thereafterdegreased in an N₂ atmosphere at 400° C., and thereafter fired in an Arinactive atmosphere at about 1550° C. to obtain the segments of thehoneycomb structure. The obtained four segments were bonded using amixture of aluminosilicate, silicon carbide powder, silica sol, andinorganic binder, and dried/hardened at 200° C. to obtain a columnarhoneycomb structure for the DPF. Characteristics of the obtainedhoneycomb structure are shown in Table 1.

TABLE 1 Composition SiC80%, Si20% Thermal expansion coefficient  4.1 (40to 800° C.) (×10⁻⁶/° C.) Porosity (%) 45 Average pore diameter (μm) 12Thermal conductivity 20 Bend strength (MPa) 20

EXAMPLE 2

A columnar honeycomb structure for DPF including the flow channelseparator shown in FIG. 8 and having the same size as that of thestructure obtained in Example 1 was prepared in the same manner as inExample 1.

EXAMPLE 3

The puddle was prepared in the same manner as in Example 1, and anintegral extruded/molded material (non-segmented molded material)including a cross-shaped 500 μm flow channel separator shown in FIG. 9was molded (integral forming method). The material was dried, clogged,degreased, and fired in the same manner as in Example 1 except that thesealing method was not used, and the columnar honeycomb structure forDPF having the same size as that of the structure obtained in Example 1was obtained.

COMPARATIVE EXAMPLE 1

The columnar honeycomb structure for DPF having the same size as that ofthe structure obtained in Example 1 as shown in FIGS. 10( a) and 10(b)was obtained in the same materials and methods as those of Example 1except that the flow channel separator was not disposed.

EXAMPLE 4

The honeycomb structure for DPF was obtained in the same materials andmethods as those of Example 1 except that a segment having a squaresectional shape with one side of 58 mm as shown in FIG. 11 was used as abasic segment and the flow channel separator having a width of 500 μmwas formed by the integral forming method shown in FIG. 2( c).

EXAMPLE 5

The columnar honeycomb structure for DPF having the same size as that ofthe structure obtained in Example 4 was obtained in the same materialsand methods as those of Example 4 except that the flow channel separatorhaving a width of 500 μm was formed as shown in FIG. 12.

EXAMPLE 6

The columnar honeycomb structure for DPF having the same size as that ofthe structure obtained in Example 4 was obtained in the same materialsand methods as those of Example 4 except that the flow channel separatorwas formed by the sealing method as shown in FIG. 13.

COMPARATIVE EXAMPLE 2

As shown in FIGS. 14( a) and 14(b), the columnar honeycomb structure forDPF having the same size as that of the structure obtained in Example 4was obtained in the same materials and methods as those of Example 4except that the flow channel separator was not disposed.

EXAMPLE 7

The honeycomb structure for DPF was obtained in the same materials andmethods as those of Example 1 except that the segment having a squaresectional shape with one side of 35 mm was used as the basic segment asshown in FIG. 15 and the flow channel separator having a width of 500 μmwas formed by the integral forming method as shown in FIG. 2( c).

EXAMPLE 8

The columnar honeycomb structure for DPF having the same size as that ofthe structure obtained in Example 7 was obtained in the same materialsand methods as those of Example 7 except that the flow channel separatorwas formed in the sealing method as shown in FIG. 16.

COMPARATIVE EXAMPLE 3

As shown in FIGS. 17( a) and 17(b), the columnar honeycomb structure forDPF having the same size as that of the structure obtained in Example 7was obtained in the same materials and methods as those of Example 7except that the flow channel separator was not disposed.

The honeycomb structures for DPF obtained in Examples 1 to 8 andComparative Examples 1 to 3 were each connected to an exhaust tube of adirect-injection three-liter diesel engine, 30 ppm of a light oilcontaining a Ce fuel additive manufactured Rodea Co. was used to run theengine, and 5 g/liter of soot was accumulated in the honeycombstructure. Thereafter, an exhaust gas temperature was raised at 500° C.or more by post injection to subject the soot to a reproductiontreatment. At this time, a maximum temperature on an outlet side in theDPF was measured, and it was checked with an optical solid microscopewhether or not any crack was made in the DPF after the test. The resultis shown in Table 2.

TABLE 2 Maximum temp. Presence/absence No. in DPF of crack ComparativeExample 1 980° C. Present Example 1 780° C. Absent Example 2 810° C.Absent Example 3 770° C. Absent Comparative Example 2 880° C. PresentExample 4 748° C. Absent Example 5 708° C. Absent Example 6 750° C.Absent Comparative Example 3 765° C. Absent Example 7 695° C. AbsentExample 8 715° C. Absent

In comparison of Comparative Example 1 with Examples 1 to 3, thehoneycomb structure obtained in Comparative Example 1 had a high maximumtemperature, and the cracks were generated. On the other hand, in thehoneycomb structures obtained in Examples 1 to 3, the maximumtemperature was controlled to be low, and any crack was not found. Incomparison of Comparative Example 2 with Examples 5 to 6, the honeycombstructure obtained in Comparative Example 2 had a high maximumtemperature, and the cracks were generated. On the other hand, in thehoneycomb structures obtained in Examples 4 to 6, the maximumtemperature was controlled to be low, and any crack was not found.

In comparison of Comparative Example 3 with Examples 7 and 8, in thehoneycomb structure obtained in Comparative Example 3, any crack was notfound, but the maximum temperature was high. On the other hand, in thehoneycomb structures obtained in Examples 7 and 8, the maximumtemperature was controlled to be low.

INDUSTRIAL APPLICABILITY

As described above, in a honeycomb structure of the present invention,since a flow channel separator is formed, the structure is notsegmented, or a smaller number of segments are integrated, so that alocal temperature rise is suppressed, and breakage by a thermal stressat the time of use does not easily occur. Furthermore, by the use of amethod of manufacturing the honeycomb structure of the presentinvention, the flow channel separator can comparatively easily beformed.

1. A honeycomb structure, comprising: a large number of cellspartitioned by cell walls and extending through an axial direction, anda flow channel separator, the flow channel separator being an insulatinglayer that extends in the axial direction, separates one group of cellsfrom another group of cells, substantially prevents a fluid that is tobe treated by the honeycomb structure from flowing through the flowchannel separator, and substantially prevents heat from passing throughthe flow channel separator.
 2. The honeycomb structure according toclaim 1, wherein at least an inflow port end is sealed to form the flowchannel separator.
 3. The honeycomb structure according to claim 1,wherein a thermal expansion coefficient at 20° C. to 800° C. is 2×10⁻⁶/°C. or more.
 4. The honeycomb structure according to claim 1, wherein aplurality of honeycomb structural segments are integrated to constitutethe honeycomb structure, and the flow channel separator is formed in atleast one of the honeycomb structural segments.
 5. The honeycombstructure according to claim 4, wherein the honeycomb structure includesa honeycomb structural segment in which a sectional area of the cell ina vertical direction is in a range of 900 mm² to 10000 mm².
 6. Thehoneycomb structure according to claim 4, wherein a bonding materialwhose difference from the honeycomb structural segment in the thermalexpansion coefficient is 1.5×10⁻⁶/° C. or less is used to bond andintegrate the honeycomb structural segments.
 7. The honeycomb structureaccording to claim 1, comprising: as a main component, one or two ormore materials selected from a group consisting of silicon nitride,silicon carbide, a silicon-silicon carbide based composite material,mullite, a silicon carbide-cordierite based composite material, andalumina.
 8. The honeycomb structure according to claim 4, comprising: asa main component, one or two or more materials selected from a groupconsisting of silicon nitride, silicon carbide, a silicon-siliconcarbide based composite material, mullite, a silicon carbide-cordieritebased composite material, and alumina.
 9. A method of manufacturing thehoneycomb structure according to claim 1 comprising a large number ofcells partitioned by cell walls and extending through an axialdirection, wherein a flow channel separator is formed, the methodcomprising: forming the honeycomb structure, and forming the flowchannel separator by extrusion.
 10. A method of manufacturing thehoneycomb structure according to claim 4 comprising a large number ofcells partitioned by cell walls and extending through an axialdirection, wherein a flow channel separator is formed, the methodcomprising: forming the honeycomb structure, and forming the flowchannel separator by extrusion.
 11. A method of manufacturing thehoneycomb structure according to claim 1 including a large number ofcells partitioned by cell walls and extending through an axialdirection, wherein a flow channel separator is formed, the methodcomprising: forming the honeycomb structure, and forming the flowchannel separator by clogging.
 12. A method of manufacturing thehoneycomb structure according to claim 4 including a large number ofcells partitioned by cell walls and extending through an axialdirection, wherein a flow channel separator is formed, the methodcomprising: forming the honeycomb structure, and the flow channelseparator by clogging.